As I write this in January of 2011, the traditional genus "Psathyrella" is headed for some pretty big changes--so by the time you read this the picture may have changed substantially. For the time being, however, Psathyrella is still a fairly large genus of saprobic gilled mushrooms with dark spore prints (ranging from brown to black or dark purplish gray), "snap-able" stems, and frequently hygrophanous caps (meaning the caps often change color dramatically as they lose moisture, sometimes resulting in two-toned specimens). The gills are neither mottled, nor do they dissolve into black goo when mature. Under the microscope, species of Psathyrella have spores that are brown or dark gray when mounted in KOH and feature smooth walls, as well as an apical pore. The pileipellis is hymeniform or "cellular."

The border line between Psathyrella and Panaeolus has always been confusing, even before contemporary DNA studies (see the linked page for more information), and we are learning that some species of Psathyrella are more closely related to coprinoid mushrooms in the genera Coprinellus and Coprinopsis than they are to some other species of Psathyrella. This cladogram (in Matheny and collaborators, 2006) represents a recent phylogenetic snapshot of the genus (scroll to the Psathyrellaceae clade); for more detailed analyses see Vasutova and collaborators, 2008 (citation below) and Padamsee and collaborators, 2008.

Identification of Psathyrella species is not easy, and generally requires microscope work. Crucial macroscopic features include the disposition of the veil remnants, and the size of the mushrooms. Microscopic features include spore morphology and, especially, the morphology of the hymenial cystidia; a Roman aqueduct section mounted in KOH (2%) is generally sufficient for working with Psathyrella specimens.

In North America over 400 species of Psathyrella have been recorded by Alexander Smith (1972). Many of these, to be honest, represent "species" collected by Smith (often only once) and differentiated on erudite microscopic features--species that may or may not be upheld once someone focuses on the genus on our continent in a contemporary way. Since major species and species groups in North America still largely bear European species names, it is also useful to consult European keys and treatments of the genus (see the reference list below).